Abolished phosphorylation of proteins in Pdk1^−/−MKs critical to MK actin cytoskeleton organization and polarization. (A) Representative immunoblot of phosphorylation levels of actin cytoskeleton regulating proteins PAK1/2 at Thr^423/402, LIMK1 at Thr⁵⁰⁸, cofilin at Ser³, and atypical PKCζ at Thr⁴⁰¹ in wild-type (Pdk1^fl/fl) and Pdk1^−/− MKs (n = 5). (B) Arithmetic means ± SEM (n = 5, unpaired 2-tailed Student t test) of blot densities actin cytoskeleton regulating proteins in wild-type (Pdk1^fl/fl) and Pdk1^−/− MKs quantified as ratio of phospho to total protein and calculated as percentage of control. **P < .01 indicates statistically significant differences.